Loudspeaker cone suspension



Oct. 27, 1964 A. F. PETRlE LOUDSPEAKER cows SUSPENSION Original FiledSept. 28, 1959 United States Patent Office 3,154,173 LGUDSPEAKER CONESUSPENSION Adelore F. Petrie, Camillus, N.Y., assignor to Generaliectric Company, a corporation of New York Original application Sept.28, 1959, Ser. No. 842,624, new Patent No. 3,072,213, dated Jan. 8,1963. Divided and this application Nov. 19, 1962, Ser. No. 246,850

2 Claims. (Cl. 181-32) This invention relates to loudspeakers, andparticularly to cone suspension arrangements for supporting the cone ofa loudspeaker.

This is a division from patent application Serial No. 842,624, filedSeptember 28, 1959, and issued as Patent No. 3,072,213.

Loudspeakers employ a cone or diaphragm arranged to be vibrated inaccordance with electrical signals, so as to convert the electricalenergy into sound or acoustical energy. The cone or diaphragm must besuspended in a manner that will permit it to be vibrated along an axis.In a typical loudspeaker, the cone is supported at its outer rim by anarrangement of concentric corrugations arranged to permit the cone tovibrate axially but not laterally. A second suspension, of smaller size,is attached to the cone near the apex thereof.

The cone suspension must be designed carefully, because it affects theoperation of the loudspeaker. For example, the suspension must besufficiently loose or compliant so that the cone can vibrate freely toproduce the desired sound waves. On the other hand, the suspension musthave sufficient stiffness to insure that the cone excursions will besymmetrical with respect to a neutral position.

It has been found that an undesirable effect is caused by theconventional suspension system. This undesirable effect is caused by aresonant condition of the suspension, whereby one or both of thesuspensions are driven into self-resonance by the vibrating cone. Thisself-resonance of the suspension system is more pronounced at certainfrequencies of self-resonance. This self-resonance condition causesundesirable distortion of the sound output of the loudspeaker. There arebelieved to be other effects that cause further distortion, due toacoustical energy from the resonating suspension system traveling downthe sides of the cone, thereby causing undesired extraneous vibrationsin the cone. Although the distortion caused in a loudspeaker by theself-resonance of the suspension system is undesirable, hitherto therehas been no satisfactory way known to reduce or minimize thisundesirable effect.

An object of this invention is to loudspeaker.

Another object is to provide a cone suspension which reduces oreliminates the above-mentioned undesirable distortion caused byself-resonance of the suspension system.

Still another object is to provide a cone suspension arrangement inwhich the frequency of self-resonance is raised, thereby the undesirabledistortion effects of self-resonance. Other object will be apparent fromthe following disclosure and from the claims, and from the drawing inwhich:

FIG. 1 is a front View of a loudspeaker embodying the present invention;

FIG. 2 is a side view, partially broken away, of FIG.

provide an improved FIG. 3 is an enlarged detailed cross-sectional viewof the cone suspension of the loudspeaker of FIGS. 1 and 2, and

FIGS. 4, 5, and 6 are detailed cross-sectional views of alternative conesuspensions in accordance with the present invention.

Patented Oct. 27, 1964 The invention comprises a loudspeaker conesuspension in the form of concentrically arranged corrugations ofresilient material, these corrugations being so shaped and arranged thatthere is less material in the central region of the suspension than atthe end regions of the suspension.

Now referring to FIGS. 1 and 2, there is shown a loudspeaker comprisinga frame 11 having an outer rim 12, and an inner rim or flange 13 towhich a magnet as sembly 14 is attached. The magnet assembly 14 maycomprise a front plate 16 attached to the flange 13, acylindrical-shaped permanent magnet 17 having an end thereof positionedagainst the front plate 16, a rear plate 18 positioned against the otherend of the permanent magnet 17, and a core 19 extending from the rearplate 13 and into an opening in the front plate 16. This structureprovides a fixed radial magnetic field in an annular gap between thecore 19 and the front plate 16.

A cone 23 is attached to the him 12 by means of an outer suspension 24-which will be described in greater detail hereafter. Preferably, thecone 23 and suspension 24 are made from treated paper. The outer edge ofthe suspension 24 is cemented to the rim 12, and a gasket ring 25 iscemented thereover. A cylindrical voice-coil form 26 is attached to thecone 23 near the apex thereof, and extends into the gap 21. A voice-coilwinding 27 is positioned on the form 26 at the gap 21, and the ends ofthis winding are brought out to a pair of terminals 28, of which onlyone is shown in the drawing. A dust cap 29 is attached to the cone 23 infront of the voice coil form 26, and an inner suspension 31 ofimpregnated cloth or other suitable material is positioned between theframe 11 and the voice coil form 26 or the cone 23 near the apexthereof.

When suitable electrical signals are applied to the terminals 28, thesesignals being supplied by an audio amplifier or other suitable source,these signals create an electrical field at the winding 27 which reactswith the magnetic field in the gap 21 so as to cause the cone 23 tovibrate in accordance with the electrical signals. This vibration of thecone 23 is in the direction of the axis thereof. The cone suspensions24- and 31 insure that the cone will vibrate axially and not laterally.

Now considering the cone suspensions, which each comprise a sheet-likeresilient material such as paper or cloth for-med into a concentricarrangement of corrugations, I have found that the desired vibrations ofthe cone 23 cause certain undesired vibrations in the corrugations ofthe suspensions. Further, I have found that the centermost corrugationsof the suspensions have a tendency to vibrate at self-resonantfrequencies, and that this vibration of the centermost corrugations atself-resonant frequencies causes undesirable distortion of the soundproduced by the loudspeaker. I have further found that this undesirableself-resonant condition of a suspension can be minimized, and theself-resonant frequencies can be raised to a value where they do notcause distortion, if the concentric corrugations of the suspension arearranged and proportioned so that their is relatively less suspensionmaterial in the central region of the suspension than at the end regionsthereof. The invention is particularly important with respect to theouter suspension 24, and also may be used advantageously with respect tothe inner suspension 31.

Now referring to FIG. 3, which is a cross-sectional View of a preferredembodiment of the cone suspension in accordance with the presentinvention, it will be seen that the outermost corrugation 35 isrelatively the largest, the next corrugation 36 is relatively smaller,the following corrugation 37 is relatively the smallest, and the nextand innermost corrugation 38 is relatively larger than the smallestcorrugation 37. This arrangement provides relatively less material inthe central region 32 of the suspension than at the end regions 33 and34 of the suspension, whereas the distribution of the material would beuniform if each corrugation was of identical size and shape. Thisarrangement reduces the tendency of the centermost corrugations 36 and37 to vibrate at their own. self-resonant frequencies, because thesecorrugations are relatively stiffer by the aforesaid construction. Theaforesaid reduction of the amount of material at the centerinostcorrugations 36, 37 not only functions to reduce a tendency toward aself-resonant condition of these corrugations when vibrated at certainfrequencies due to vibrations of the cone 23, but it also tends to raisethe frequency of resonances of these center corrugations 36 and 37,thereby minimizing the disturbing effects of self-resonance. The sameprinciple can be applied to a suspension having a greater or smallernumber of corrugations.

FIG. 4 illustrates how a suspension system can'be improved, inaccordance with the invention, by making one or more of the centermostcorrugations 40 a shorter height than the end corrugations 41 and 42,thus decreasing the amount of material in the center region of thesuspension.

FIG. illustrates how the centermost corrugation 4-0 can be given arelatively larger radius than that of the end-most corrugations 411 and42, thereby reducing the amount of material at the center region of thesuspension.

FIG. 6 illustrates an arrangement in which the sides M, 45 of thecentermost corrugation 40 are provided with more gradual slopes than arethe sides 46, 47 of other corrugations of the arrangement therebyeffectively reducing the amount of material in the centermost region ofthe suspension.

Any of the above-described arrangements for reducing the amount ofmaterial in the central region of a suspension can be combined together,and also can be applied to either or both of the outer suspension 24 andthe inner suspension 31 of a loudspeaker.

From the foregoing it should readily be appreciated that I have provideda simple, economical and beneficial new design and construction for aloudspeaker suspensions, which, by providing relatively less material atthe central corrugations than at the end corrugations of the suspension,causes a reduction in mass in this central region, and thus I reduce thetendency for undesirable self-resonance to occur in the suspensionsystem, and I also increase the frequency of any self-resonantcondition. The new suspension arrangement of this invention greatlyreduces or prevents a self-resonant condition of the suspension andthereby reduces or prevents an undesirable distortion eifect which hasplagued loudspeaker designers.

While preferred embodiments of the invention have been shown anddescribed, various other embodiments and modifications will be apparentto those skilled in the art, but will fall within the scope of inventionas defined in the following claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A loudspeaker cone suspension comprising resilient material shaped toprovide at least three concentrically arranged symmetrical corrugationsin the outermost region there-of, each of said corrugations including atleast one substantially curved portion of a predetermined radius ofcurvature, the curved portions of the three corrugations facing in thesame general direction, at least one of the intermediate corrugationshaving a curved portion of a radius of curvature which is greater thanthe radii of curvature of the end corrugations.

2. A loudspeaker cone comprising a conically shaped member of resilientmaterial provided with at least three concentrically arrangedsubstantially curved corrugations in the outermost region thereof, afirst one of said corrugations being an outermost corrugation, a secondone of said corrugations being an innermost corrugation, and a third oneof said corrugations disposed between said first and second corrugationsand having a radius of curvature which is greater than the radius ofcurvature of the first and second corrugations, thereby to raise thefrequency of self-resonance for said corrugations.

References Cited in the file of this patent UNITED STATES PATENTS

1. A LOUDSPEAKER CONE SUSPENSION COMPRISING RESILIENT MATERIAL SHAPED TOPROVIDE AT LEAST THREE CONCENTRICALLY ARRANGED SYMMETRICAL CORRUGATIONSIN THE OUTERMOST REGION THEREOF, EACH OF SAID CORRUGATIONS INCLUDING ATLEAST ONE SUBSTANTIALLY CURVED PORTION OF A PREDETERMINED RADIUS OFCURVATURE, THE CURVED PORTIONS OF THE THREE CORRUGATIONS FACING IN THESAME GENERAL DIRECTION, AT LEAST ONE OF THE INTERMEDIATE CORRUGATIONSHAVING A CURVED PORTION OF A RADIUS OF CURVATURE WHICH IS GREATER THANTHE RADII OF CURVATURE OF THE END CORRUGATIONS.